Vol. 20, No. 39
THE JOHNS HOPKINS MICROBIOLOGY NEWSLETTER
Tuesday, September 25, 2001
A. Provided by Leslie Edwards Reger, Division of Outbreak Investigation, Maryland Department of Health and Mental Hygiene.
No information available.
B. The Johns Hopkins Hospital, Department of Pathology. Information
provided by Anil V. Parwani, M.D., Ph.D.
Case Report
TC is a 5-year-old white male who presented with a 1-week history of bloody diarrhea to his pediatrician. A stool culture and a C.difficile toxin assay were performed. He was brought to an outside hospital ED where he was treated with cefixime and discharged. Subsequently, he was admitted to the outside hospital with worsening symptoms. The C.difficile toxin assay was positive and oral metronidazole was started. A repeat C.difficile toxin assay was negative. The patient continued to have bloody diarrhea and emesis. Metronidazole was discontinued and azithromycin was started for presumptive Campylobacter colitis. TC was transferred to JHH for further management. On admission, he was tachycardic (P:121) with a pale appearance and mild jaundice. Admission labs: Hct: 21.2, Hb:9, Plt:33, WBC:14.8, CK:159, LDH:4690, Cr:3.0, BUN:52, ALT:92, AST:266. Urinalysis revealed 3-5 WBC, 5-10 granular casts, and 4+ protein. The patient was diagnosed with hemolytic–uremic syndrome (HUS). Hospital course was significant for worsening renal function which required hemodialysis and progressive hemolysis which required pRBC transfusions. Repeat C.difficile toxin assay at JHH was negative. Stool cultures at JHH were positive for the presence of Shiga-like toxin (SLT) by immunoassay and SLT producing E. coli 0157:H7. The patient’s younger sister also developed bloody diarrhea four days after TC’s illness began. She developed hematuria, thrombocytopenia and elevated BUN/Cr. She was also admitted to JHH, transferred to PICU and eventually required hemodialysis. Her stool culture was also positive for the presence of Shiga-like toxin (SLT) by immunoassay and SLT producing E. coli 0157:H7.
E. coli 0157:H7
Organism and Clinical spectrum: E.coli is a facultative
anaerobic gram-negative bacillus, which is a major component of the normal
intestinal flora. E.coli is a common cause of urinary tract infections,
and neonatal sepsis and meningitis. Shiga toxin producing E.coli
(STEC) cause a wide variety of diseases including HUS, hemorrhagic colitis,
renal failure, bloody or non-bloody diarrhea. HUS is an often devastating
result of enteric infection with some strains of E.coli and consists
of the triad of renal failure, microangiopathic hemolytic anemia and thrombocytopenia.
HUS usually develops in the second week of the illness and typically by
this time the diarrhea has resolved, making it difficult for the organism
to be isolated from stool culture. The typical presentation is weakness,
irritability and oligouria. Some patients may develop fever. The duration
of illness is from 4 to 12 days.
Epidemiology: Recent data indicate that more than 100,000 cases of illness are attributable to STEC, a majority of which are strains other than 0157:H7. The mortality and morbidity rates in infants and elderly are high. Cattle are a primary reservoir of STEC strains. Transmission is by fecal-oral route and outbreaks have been associated with undercooked beef, dairy products, apple cider and contaminated water. Recent reports have linked STEC organisms to 21 cases of diarrheal disease contracted at a petting zoo in Pennsylvania. To date, E.coli 0157:H7 has been one of the most commonly reported serotypes of STEC. CDC recommends that all stools submitted for routine stool culture be examined for the presence of E.coli 0157:H7. The cumulative number of 2001 E.coli 0157:H7 cases reported by CDC via the National Electronic Telecommunications System for Surveillance (NETSS) up to the week ending September 9, 2001 were 1695. The NETSS E.coli 0157:H7 cumulative cases for 2000 were 3060. The incidence is increased in the summer months and early fall. It is estimated that in the U.S there are 0.3-10 cases of HUS per 100,000 children.
Diagnosis: Current methods for detection of STEC strains include culture on sorbitol MacConkey plates. This is useful because most 0157:H7 strains ferment sorbitol slowly. This method does not detect other serotypes of STEC. The culture method is of low yield after 1 week of diarrhea. Other methods include enzyme immunoassays, or latex agglutination assays either directly on stool specimens or after broth amplification. Presence of fecal leukocytes is variable.
Treatment: Treatment for HUS is supportive and early recognization and careful management of fluids and electrolyte balance are instrumental in successful management of HUS patients. Antibiotic treatment for HUS is usually not indicated and should be avoided. Systemic infections such as sepsis and bacteremia are treated with appropriate intravenous antibiotics. Up to 10% of patients may develop chronic renal failure. Early dialysis is often associated with a better outcome.
References: